Apparatus for applying liquid to articles without touching the articles

ABSTRACT

Coating fluid is applied to an article, without contacting a body of the article with means other than the fluid to be applied. An applicating member, having at least one tooth with a concavity therein, is dipped into a bath of coating fluid, retracted and fluid retained in and about the concavity by capillarity. The member is then brought into noncontacting relation with the article so that a portion of the article lies within the fluid-filled concavity. A quantity of fluid within the concavity contacts and flows about the article, coating it. Simultaneous coating of a plurality of paramagnetic-leaded electrical devices utilizes magnetic holding of the devices, luring the coating process, and an applicator with a plurality of spaced teeth arranged in a comblike array.

United States Patent [191 Blewett et al.

APPARATUS FOR APPLYING LIQUID TO ARTICLES WITHOUT TOUCHING THE ARTICLESInventors: John H. Blewett, Reading; Harry K. Naumann, Wernersville,both of Pa.

Assignee: Western Electric Company,

Incorporated, New York, NY.

Filed: Aug. 5, 1970 Appl. No.: 61,504

Related U.S. Application Data Division of Ser. No. 744,082, July 11,1968, Pat. No. 3,589,938.

References Cited k UNITED STATES PATENTS 3,010,427 11/1961 Hautau178/243 3,043,721 7/1962 Burns 118/221 X FOREIGN PATENTS OR APPLICATIONS447,923 4/1948 Canada 118/421 Primary Examiner.lohn P. McIntosh Attorney-R. Y. Peters [57] ABSTRACT Coating fluid is applied to anarticle, without contacting a body of the article with means other thanthe fluid to be applied. An applicating member, having at least onetooth with a concavity therein, is dipped into a bath of coating fluid,retracted and fluid retained in and about the concavity by capillarity.The member is then brought into noncontacting relation with the articleso that a portion of the article lies within the fluidfilled concavity.A quantity of fluid within the concavity contacts and flows about thearticle, coating it. Simultaneous coating of a plurality ofparamagneticleaded electrical devices utilizes magnetic holding of thedevices, luring the coating process, and an applicator with a pluralityof spaced teeth arranged in a comblike array.

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SHEET 0; HF 12 PATENTEU 53974 3.785.341

saw us nr12 PATENTEDJAN 1 5!.314

sum 10 ur1z PATENIE JAN 1 5 I974 sum 11 0F12 SPEED CONTROL MAGNET LIFTCAM H8 VARNISH COMB DWELL DWELL M DOWN MOVES ggwif M82455 DIP CAM COMBMOVES OVER DWELL= TO VARNISH COMB MOVES OVER TO VARISTORS TRANSFER DWELLOVES COMB

' COMB CARRIAGE DWELL hfigvg Y DOW N DWELL O COMB CAM H6 LIMITSWITCHRACK l5] CLOSED SWITCH OPEN 'ADVANCE CAM I49 PATENTEU JAN 1 5 I974 sum12 or 12 744,082, filed July 11,

APPARATUS FOR APPLYING LIQUID TO ARTICLES WITHOUT TOUCHING THE ARTICLESThis application is a division of application Ser. No. I968, now US.Pat. No. 3,589,938.

BACKGROUND OF THE INVENTION This invention relates generally toapparatus for applying liquid coatings to articles. In a specificexample, the invention relates to applying a protective varnish coatingto each of a multiplicity of varistors, simultaneously andautomatically, without contacting the varistors other than the coatingmaterial. Accordingly, the general objects of the invention are toprovide new and improved apparatus for such purposes.

In the past, a protective junction-coating resin, hereinafter calledvarnish, was applied to electrical devices, such as varistors, by meansofa hypodermic needle and syringe. With the syringe filled, an operatorforced a a small amount of the varnish out of the handheld syringe anddirected it at the varistors, one at a time. One disadvantage of thistechnique is that the amount of varnish exuded from the syringe dependson the operators sense of feel and may vary from varistor to varistor aswell as from operator to operator.

Another disadvantage is that the operators would frequently touch thevaristors with the end of the hypodermic needle and cause contaminationof or possible damage to the varistor.

Still another disadvantage is the slow speed of manually applying thevarnish to the varistors one by one. Accordingly, specific objects ofthis invention are to overcome the aforementioned problems anddisadvantages by providing new and improved apparatus for applyingcontrolled amounts of varnish to a plurality of varistors withoutcontacting them.

Other objects are to provide new and improved apparatus:

l for applying a liquid coating, such as varnish, in such a way that theliquid is caused to flow around the article being coated;

2 for applyingsuch a coating to a multiplicity of articlesautomatically; and

3 for applying the coating to the articles without touching them.

SUMMARY The foregoing and other objects are accomplished, in accordancewith certain features of the invention, by providing an applicatormember having a concave recess, in one surface, of a size somewhatlarger than a portionof an article to be coated. First, the applicatoris engaged with a coating liquid such that a quantity of the liquid isretained in the recess by capillary action. Then, the applicator memberand article are brought into close, noncontacting proximity, so that therecess surrounds a portion of the article to be coated and the liquidcontacts the article. The liquid then flows from the applicator memberonto the article, to coat the article without touching it with theapplicator member.

In specific embodiments of the invention, the applicator member isdipped into a bath of coating liquid, to coat both the recess andsurrounding portions of the member, and is brought into proximity to anarticle to be coated so that liquid flows onto the article both from therecess and the surrounding portions of the member.

Preferably, the article is held down during application of the liquid.For simultaneous coating of many articles, and/or spaced portions of onearticle, a plurality of the applicator members are arranged in acomblike array of teeth on an elongated support member. Preferably, theteeth are spaced by slots, which are longer than the depth of immersionof the teeth in the coating liquid, to prevent liquid from flowing fromone tooth to the next. In accordance with a specific embodiment, forautomatically applying varnish to a plurality of varistors, apparatus isprovided for automatically extracting racks of varistors from acanister, guiding the racks to a varnish-applying station, applyingvarnish simultaneously to all varistors in the rack, and inserting therack of coated varistors into another canister. The varistors rest inevenly spaced notches, formed along the length of the racks, and areheld down magnetically during the coating operation.

Other objects, advantages and features of the invention will be apparentfrom the following detaileddescription of specific examples andembodiments thereof.

BRIEF DESCRIPTION OF THE DRAWINGS In the accompanying drawings:

FIG. 1 is an isometric view of a coated varistor;

FIGS. 2 and 3 are front and end elevations, respectively, of the coatedvaristor;

FIG. 4 is an isometric view of a rack loaded with unvarnished varistors;

FIG. 5 is an isometric view, with portions broken away, showing theoverall arrangement of the major machine components;

FIG. 6 is an end elevation, with two racks shown in phantom, of acanister from which the racks of uncoated varistors are withdrawn,viewed along line 6-6 of FIG. 5;

FIG. 7 is a front elevation of the same apparatus, viewed along line 7-7of FIG. 6;

FIG. 8 is a front cross-section along line 8-8 of FIG. 5, with thecanister removed, illustrating a station for unloading the racks from acanister;

FIG. 9 is a partial end elevation of the same apparatus, viewed alongline 9-9 of FIG. 8;

FIG. 10 is a plan view of the transfer table, viewed along line 10-10 ofFIG. 5;

FIG. 11 is a front elevation of the same mechanism, viewed along line11-11 of FIG. 10;

FIG. 12 is a cross-section taken along line 12-12 of FIG. 11;

FIG. 13 is a rear elevation of the varnish-applying station, viewedalong line 13-13 of FIG. 5;

FIG. 14 is a cross-section viewed along line 14-14 of FIG. 13;

FIG. 15 is a cross-section of the varnish-applying station motor drive,viewed along line 15-15 of FIG. 13;

FIG. 16 is an isometric view of a portion of the varnish-applying comb,showing the relation of the comb to a varistor at the time of varnishapplication;

FIGS. 17 and 18 are front and end views, respectively, of one pair ofapplicator teeth, with portions of FIG. 18 broken away for clarity;

FIG. 19 is an isometric view of the load station, partly incross-section, for returning the racks to a canister;

FIG. 20 is a schematic drawing of an electrical control circuit;

FIG. 21 is a cam timing chart; and

FIG. 22 is a schematic drawing of a pneumatic circuit.

DETAILED DESCRIPTION In the following detailed description ofa specificembodiment of the invention, the process to be performed will bedescribed generally with reference to FIGS. 1-4, following which therelation among the major component mechanisms of an automatic machinefor performing the process will be described with reference to FIG. 5.After that, the specific method steps and the mechanical movements ofeach mechanism will be described separately, in the sequence in whichthey perform the process, with reference to FIGS. 6 through 19. Finally,the operation of the complete machine will be described with referenceto the control circuits and mechanisms illustrated schematically inFIGS. -22.

PROCESS PERFORMED Referring to FIGS. 1-3, a coated varistor 31 inaccordance with the invention consists of two parallel, overlapping wireleads 32-32 (of solder-coated, copperplated steel), between which twoback-to-back semiconductor diode chips 33-33 have been soldered. As bestseen in FIGS. 2 and 3, the chips 33-33 plus the entire area where theleads overlap is coated with a varnish 34, such as Dow CorningSemiconductor Junction Coating Resin type XR-61-043-A. This resin isafairly viscous fluid having a consistency similar to ordinary varnish,of the order of 100 to I50 centipoise at C. The varnish must flow aroundand coat the entire exposed surfaces of both diode chips, as well asflow into a generally rectangular space 35 between the chips.

Referring to FIG. 4, a plurality of uncoated varistors 36-36 (fifty inthe specific example) are placed in a rack 37 which holds them in anaccurately spaced relationship for the coating process. The rack 37consists of two notched sides 38-38, having aligned notches 39-39 forsupporting the varistor leads 32-32, and front and rear tie rods 41-42for holding the sides together. The varnish coating 34 is applied to allthe uncoated varistors 36-36 in the rack 37 simultaneously, withouttouching the uncoated varistors with the varnish-applying mechanism and,as a consequence, without contaminating or damaging the varistors.

RELATION AMONG MAJOR MACHINE COMPONENTS A complete varnish-coatingapparatus 43, as shown in overall outline in FIG. 5, is comprised of anunloading station 44 connected to a loading station 46 by a racktransfer table 47. A varnish-applying station 48 is placed at anappropriate position on the transfer table 47, between the unload andload stations, and a panel 49 with the electrical controls is positionedto the rear of the rack-transfer table 47. Pneumatic and electricalcircuits to air cylinders and an electric motor complete the apparatus.

A canister 51, containing a supply of vertically stacked racks 37-37 ofuncoated varistors is placed in position on the unloading station 44.The lowermost rack 37 is released by escapements 52-52 and is loweredinto alignment with guide tracks 53-53 on the transfer table 47, so thatit is in a position to be engaged by a rcciprocable transfer bar 56.When the transfer bar 56 is shifted to the left, it engages one of theracks 37 and, when next shifted to the right, draws it from the canisteronto the guide tracks 53-53. Successive operations of the transfer bar56 withdraw additional racks from the canister 51 and, at the same time,push the preceding racks along the guide tracks 53-53 beneath thevarnish-applying station 48 and finally into a canister 51 on the loadstation 46.

The transfer bar 56 moves from left to right and back again, as viewedin FIG. 5. During the return stroke and the following pause, the varnishcoating 34 is applied at the varnish-applying station 48. Thevarnishapplying station 48 is operated in synchronism with the cycle ofthe transfer bar such that one rack of uncoated varistors is coated foreach cycle of the transfer bar 56. Specifically, completion of the cycleof the transfer bar 56 initiates the varnish application, and completionof the varnish application initiates the next transfer bar cycle.

The varnish coating 34 is applied to the uncoated varistors 36-36 bycausing an applicator member, in the specific example comprising thecomb 57 having a pair of applicator teeth 58-58 for each uncoatedvaristor in the rack 37, to be dipped into and withdrawn from a trough59 containing the varnish 34. The comb 57 is then shifted rearward, asviewed in FIG. 5, with the varnish 34 clinging to the teeth 58-58, sothat it is positioned over the varistors 36-36 resting in the the rack37. The comb 57 is then lowered toward the varistors so that the varnish34 touches the uncoated varistors 36-36, but the teeth 58-58 do not, anda predetermined amount of the varnish flows onto each varistor as willbe described in further detail hereafter. A magnet (not shown in FIG. 5)holds the varistors down in the rack 37 so that, when the comb 57 islifted and returned to the varnish trough, the varistors will not stickto it and be lifted from the rack.

When the varnishing cycle is completed, transfer of the racks 37-37 isonce again initiated. The rack 37 of varistorsjust coated is pushed frombeneath the varnish-appyling station 48 into the bottom of the loadingcanister 51'. When the rack 37 of coated varistors 31-31 is in positionwithin the canister 5lit is raised until it is held by latch mechanisms61-61 above the next rack to be pushed into the canister 51'. Thiscompletes one cycle of operation. When the canister 51 is empty, it isreplaced by a full one and when the canister 51 is full, it is replacedby an empty one.

METHODS AND MECHANICAL MOVEMENTS UNLOAD STATION Referring to FIGS. 6 and7, the canister 51, from which the racks 37-37 are unloaded, is shown;it being understood that the loading canister 51' has the sameconstruction. The canister 51 has end openings 62-62 to clear portionsof the escapements 52-52. The end openings 62-62 in the canister 51'clear portions of the latch mechanisms 61-61. The canisters 51 and 51'also have lower and wider end openings 63-63 to permit the racks 37-37to be withdrawn or inserted into the canisters. Four spaced pins 64-64support the lowermost rack 37, and thus the column of racks above, whencanisters 51 and 51' are not on the varnishcoating apparatus 43. A setof four locating holes 66-66 in the bottom sections of each canister 51serve to locate the canister precisely on the unload station 44.Specifically, as the canister 51 is placed on the unload station 44, thelocating holes 66-66 fit over a set of four correspondingly spacedmounting pins 67-67 projecting upward from a table top 68, as shownfragmentarily in phantom in FIGS. 6-7. This serves to position thecansiter 51 precisely with respect to the unloading apparatus next to bedescribed.

Referring now to FIGS. 8-9, as a canister (not shown) is first loweredinto position on the locating pins 67-67, the tie rods 41 and 42 of thelowermost rack 37 temporarily come to rest on a pair of escapementfingers 71-71 which are a part of the escapements 52-52 previouslymentioned. The canister 51 continues to descend, leaving the racks 37-37suspended on the escapement fingers 71-71, until it rests on the tabletop 68. In this position, the supporting pins 64-64 are situated at alevel below the bottom of a rack 37 when it is cradled in the racksupport guides 76-76 in their lowermost position.

When an air cylinder 72 (FIG. 8) is actuated, its piston raises racksupport rods 73-73, which pass through bearings 74-74 in the table top68 and terminate in rack support guides 76-76, until the column of racks37-37, for which the two lowermost racks are shown in phantom, is liftedslightly clear of the escapement fingers 71-71. After this, theescapement fingers 71-71 are withdrawn by air cylinders 77-77 frombeneath the rack tie rods 41 and 42 and the piston of the air cylinder72 is lowered. As it descends, and after the tie rods 41 and 42 of thelowermost rack 37' reach a position just below the withdrawn escapementfingers 71-71, the escapement fingers are returned by springs in thecylinders 77-77 to their initial positions in time to catch and supportthe next rack 37 by its front and rear tie rods 41 and42. The piston ofthe air cylinder 72 continues its downward movement, with a rack 37-37cradled in its rack support guides 76-76, until the piston reaches itslowermost position. At this point, the rack 37' is aligned with thetransfer table 47 and is ready to be pulled onto it.

Valves 78 and 79, which are shown in FIG. 8 and operate from camsurfaces 81 and 82 respectively, control the operation of the escapementfingers 71-71 and the return of the piston of air cylinder 72 to itsbottom position.

TRANSFER TABLE Referring now to FIGS. -12, the transfer table 47consists of a flat plate 83 on which the rack guides 53-53 and guardrails 84-84 are mounted. Midway between the rack guides 53-53, thetransfer bar 56 is mounted in slide bearings 87-87 (FIG. 12) which arefastened in supports 88-88. Additional supports 89-89 are provided forthe rack guides 53-53 and the guard rails 84-84. A plurality of leafsprings 90-90 (one shown in FIG. 10) are mounted at intervals along therear guide 53, to urge the racks 37-37 lightly against the front guide53 so that the racks will always be exactly positioned at thevarnish-applying station 48. The guard rails 84-84 limit axial movementof the uncoated varistors' 36-36 so that they too will be accuratelylocated at the varnish-application station 48.

The transfer bar 56 is moved from left to right and returned by thepiston of an air cylinder 91, which is connected to the transfer bar 56by a connecting link 92. A stop 93 determines the end of the stroke ofthe piston of the air cylinder 91 and permits adjusting theend-of-the-stroke position of the transfer bar 56 within the limits of astop screw 94.

The transfer bar 56 is slotted in appropriate places to receive a set offive pawls 54a-54e. The pawls 54a-54e may rotate freely about pivot pins96-96 (one shown at the left of FIG. 11), each pawl being so constructedthat its center of gravity is below the point of rotation. This causesthe pawls 54a-54e to stand with their points oriented in an upwarddirection. A plurality of stop pins 97-97 limit the rotation of pawls54a-54e to a clockwise direction as viewed in FIG. 11. Consequently,when the transfer bar 56 moves to the right, the pawls 54a-54e engagethe rack tie rods 41 or 42. Since they cannot rotate counterclockwisebecause of the stop pins 97-97, the pawls 54a-54e pull the racks 37-37along the guides 53-53 by means of the pawls engaging the tie rods 41and 42. However, when the transfer bar 56 returns to the left, the tipsof the pawls 54a-54e strike the tie rods 41 and 42, rotate clockwise(because there is nothing to prevent this), and then slide beneath thetie rods 41 and 42. Consequently, movement of the transfer bar indexesthe racks 37-37 from left to right only.

Referring now to FIG. 11, and starting with one rack 37 (shownfragmentarily in phantom) in position to be withdrawn from the canister51, the transfer bar 56 is actuated and moves its first full stroke fromleft to right. In so doing, the pawl 54a engages the front tie rod 41 ofthe first rack 37 and pulls it into position to be engaged by the pawl54b. The transfer bar 56 is returned to its starting position so that(a) the pawl 54a engages the front tie rod 41 of a second rack 37 to bewithdrawn from the canister 51 and (b) the pawl 54b engages the fronttie rod 41 of the first rack already withdrawn. The second full strokeof the transfer bar 56 to the right positions the second rack 37 in theplace formerly occupied by the first one and moves the first one intoposition so that its rear tie rod 42 can be engaged by the pawl 540. Thetransfer bar 56 is then returned leftward to its starting position. Thethird full movement of the transfer bar 56 to the right will withdraw athird rack 37 from the canister 51 and move the second rack 37 intoposition so that its rear tie rod 42 can be engaged by the pawl 54c andmove the first rack into position so that its rear tie rod 42 can beengaged by a pawl 54d. This sequence of operations continues until thepawl 54e has pushed the rear tie rod 42 of the first rack 37, andconsequently the rack itself, as far as it can to the right. At thispoint, one rack 37 is in position in the varnish-applying station 48.After coating, the racks are pushed out of the varnish-applying station48 and into the load station 46 by the following racks 37-37 ofvaristors to be coated.

At the start of the stroke of the piston of the air cylinder 91, a speedcontrol'cam 98 (FIGS. 10 and 12) holds a pilot valve 99 closed andcontinues to hold it closed until the speed control cam 98 (which ismounted on the transfer bar connecting link 92) is moved to the rightbeyond a cam follower 101. During the time the pilot valve 99 is closed,air flow is restricted and the piston of air cylinder 91 moves slowly.When the pilot valve 99 opens, the air flow restriction is removed andthe piston moves rapidly.

At the end of the stroke, when the transfer bar connecting link 92strikes the stop screw 94, the cam 98 strikes a cam follower 102 (FIG.10) and actuates another pilot valve 103. This ,admits air to the rightend of the air cylinder 91 and fully returns its piston to the left endof the air cylinder for the next cycle. An interlock limit switch 104assures that the piston has returned to-its starting position. The limitswitch must be held closed by an interlock cam 106 in order to start thenext cycle. When a limit switch 107 is actuated by the cam 106, as thereturn stroke of the piston of the air cylinder 91 is completed, itstarts the varnishapplication cycle which will be described next.

VARNISH-APPLYING STATION Referring now to FIGS. 13-15, thevarnish-applying station 48 is driven by an electric motor 108 throughdrive gears 109 and 111. The gear 111 is fastened to a driving member112, which is connected to a camshaft 113 through a single-revolution,solenoid-operated clutch 114. A comb-shifting cam 116, a varnishdippingcam 117 and a magnet-lift cam 118 are fastened to the camshaft 113.

The comb 57 is shifted by the cam 116 acting through a bell crank 121which pivots about a fixed pin 122. One end ofthe bell crank 121 has acam roller 123 which bears on the comb-shifting cam 116 and, on theother end, a cam roller 124 is mounted, which cooperates with a slot 126in a member attached to a pair of parallel comb support rods l27127. Aspring 128 holds the cam roller 123 against the cam 116 so that the endsof the bell crank 121 will follow the motion of the cam and cause thecomb 57, suspended in a comb support 127', to dwell over the varnishtrough 59 for dipping into the varnish 34 or over the varistors forapplying the varnish 34 in accordance with the comb transfer cam diagram(see FIG. 21). A timing mechanism (not shown) can be incorporated intothe system for stopping the cam shaft 113, and hence the cam 116, sothat the duration of dwell can be specifically controlled.

The comb 57 is moved up and down, in order to dip it into the varnish 34in the varnish trough 59, by means of the vanish-dipping cam 117, a camfollower 129 and a comb support carriage 131. The level of the varnish34 in the trough 59 is maintained by a varnish supply 59'. Springs132132 hold the comb-support carriage 131 and the cam follower 129against the varnishdipping cam 117, so that the comb-support carriage131 follows the motion of the cam 117. Accordingly, the comb 57 movesdown into the varnish; dwells slightly to pick up the varnish; moves upout of the varnish and dwells while it is shifted to a position over thevaristors by the comb-transfer cam 116; moves down to the varistors anddwells slightly to give the varnish time to transfer to the varistors;and finally moves up to clear the varistors, all as shown by thevarnish-dipping cam diagram in FIG. 21.

The coated varistors 31-31 tend to stick to the varnish comb 57 and tobe lifted from the rack 37 when the comb is retracted after coating. Inorder to prevent this, the varistors 31-31 (shown in FIG. 14) are helddown in the rack 37 by a channel-shaped bar magnet 148 which is as longas the comb 57. The magnet 148 is raised into position beneath thevaristors 31-31 by means of the magnet-lift cam 118, acting through abell crank 133, a connecting rod 134 with ball joints 136-136, a lever137 and a magnet-lift carriage 138. A spring 139 applies downward forceon the lever 137 and, through the connecting rod 134 and the bell crank133, holds a cam roller 141 against the cam 118 so that the magnet-liftcarriage 138 will follow the motion of the cam 118. The magnet-liftcarriage moves up to a position in close proximity to the varistors (seeFIG. 18); dwells during the application of the varnish; moves back downto clear the varistors and dwells during the rack advance according thethe magnet-lift cam diagram of FIG. 21. The bell crank 133 pivots abouta fixed pin 142, while the lever 137 pivots about a fixed pin 143 and isforked to engage a pin 144 fixed in the magnet-lift carriage 138. Thedownward movement of the connecting-rod end of the lever 137, due torotation of the cam 118, results in upward movement of the forked end ofthe lever 137 and the magnet-lift carriage, and vice-versa. The lengthof the connecting rod 134, in cooperation with the balljoints 136-136,is adjusted so that, in the extreme upward position of the magnet-liftcarriage 138, the magnet 148 is held just beneath (e.g., V; to A inchaway from) the varistors 3l31. In this position, the magnetic force isgreat enough to overcome the opposing attractive force of the varnishwhich tends to lift the varistors.

The drive motor 108 continuously rotates the driving member 112. A cam149 is a circular one attached to the cam shaft 113, as shown in FIG.15, and cooperates with a limit switch 151. The limit switch 151 is heldopen by the cam 149, except when a cam follower 152 drops into a notch153 in the cam 149 for a moment. This actuates the piston of therack-transfer air cylinder 91, which at the end of its stroke, energizesa clutch solenoid 154 through the limit switch 107. Energizing theclutch solenoid 154 actuates the single-revolution clutch 114 whichconnects the driving member 112 to the camshaft 113, and, therefore,they rotate together for one revolution.

The cams 116,117, and 118 are fixed to the camshaft 113. Theirrelationship and shape is such that, starting with the comb 57 in thevarnish 34, the cam 117 withdraws the comb 56 from the varnish 34, thecam 116 shifts the comb 57 to a position over the varistors 31--3l whereit dwells, and the cam 118 moves the magnet-lift carriage 138 upwardbeneath the varistors and dwells. During the dwell of the shift and liftcams 116 and 118, respectively, the comb-dipping cam 117 lowers the comb57 to its final position over the uncoated varistors 36-36, with theteeth 58-58 partially surrounding but not touching the varistors to coatthe varistors. Further rotation of the camshaft 113 causes; (1) the dipcam 117 to raise the comb 57, (2) the magnet-lift cam 118 to lower themagnet-lift carriage 138, and (3) the comb-shifting cam 116 to move thecomb 57 toward the right. Completion of rotation of the camshaft 113returns the comb 57 to its starting position in the varnish trough 59and the magnet-lift carriage 138 to its lowermost position.

The events which occur during varnishing of the varistors can best beunderstood by referring to FIGS. 16-18, showing the details ofconstruction of the applicator member and its relationship to thearticles being coated. In the specific embodiment, the applicator memberresembles a comb comprising an elongated horizontal body members 57-Afrom which the individual applicator teeth 58-58 project downward in twospaced, parallel rows, R1 and R2 extending in the X direction indicatedin FIG. 16. In the Y" direction, the teeth are arranged in spacedcolumns (C1, C2, etc.) of two teeth per column, running perpendicularlyto the rows. The lower faces of the teeth are flat, generallyrectangular, and lie in a common horizontal plane, as illustrated inFIG. 16.

Each individual tooth 58 is formed with a concave recess 58-A in itslower face, comprising a generally semicircular groove in the specificembodiment, running in the Y direction such that the recesses of eachpair of teeth in each column are aligned in the Y direction as shown.The recesses divide the lower face of each tooth into two parts, formingflat, rectangular land areas 58-B, 58-B, one on each side of each recessalong the X direction. The comb body is formed with a plu rality ofelongated vertical slots 57-B, 57-B, which define the teeth in each rowand isolate the teeth from each other. Also, the comb body is ofinverted U- shaped cross section, as shown in FIG. 18, which defines, ineffect, further elongated vertical slots 57-C, 57-C. These slots defineand isolate the individual teeth in each column C1, C2, etc.

As best seen in FIG. 17, each recess 58-A is large enough to encompassthe portion of the article to be coated (in the specific example, one ofthe diode chips 33-33 and the portions of the leads 32-32 solderedthereto), and is of such generally fitting curvature that the recess maybe placed over the portion of the article to be coated and surround theupper portion of the same fairly closely, without touching the article.The size and shape of a recess 58-A are two of the factors which affectthe amount of varnish that the associated tooth can carry and transferto the article being coated.

As best illustrated in FIG. 18, the width W of each tooth (also a factorwhich affects the quantity of varnish being trasferred), and thus eachrecess, is approximately the same as that of the chip 33 to be coated sothat each tooth, when lowered, covers one of the chips. For other sizesand shapes of articles to be coated, the recess is similarly made alittle larger than the article and shaped to fit fairly closely over theportion of the article to be coated. As is apparent from FIGS. 17 and18, the teeth are separated (1) in the X direction by the slots 57-B,57-B in accordance with the spacing of the uncoated varistors 36-36 inthe rack 37 (FIG. 4) such that each column of two teeth co-vers portionsof a corresponding varistor, and (2) in the Y direction by the slots57-C, 57-C in accordance with the spacing of the chips 33-33 such thatthe two teeth in each column encompass the two chips of a correspondingvaristor. In general, the number and spacing of the teeth are selectedby the number and spacing of the articles to be coated where more thanone article is coated at a time, and/or by the number of separateportions of each article to be coated, where spaced portions of eacharticle are to be coated. In the specific example, each of fiftyvaristors are simultaneously coated, with one hundred teeth beingprovided, arranged in fifty rows of two columns each.

In coating the varistors, the comb 57 is first dipped into the trough 59of varnish 34 and then raised by the lifting mechanism previouslydescribed. The depth of immersion (distance D in FIG. 16), and the rateof withdrawal are among the factors which determine the amount ofvarnish adhering to the teeth 58-58. As depicted in the drawing, fairlylarge drops or menisci of varnish are retained in the recesses bycapillary action, and a substantial additional quantity of varnish isretained on the surrounding portions of each tooth. The slots 57-8 and57-C are made longer than the maximum expected depth of immersion of theteeth (thus substantially longer than the depths of the recesses 58-A,58-A) so that the upper ends of the slots are never filled with varnish.With this arrangement, the varnish 34 is prevented from flowing from onetooth to another, ensuring that each tooth carries essentially the sameamount of varnish (for a given depth of immersion and withdrawal rate),regardless of any slight deviations from horizontal in the attitude ofthe comb 58.

As the teeth 58-58 move into proximity with the portions of the uncoatedvaristors 36-36, the varnish flows from the cavities 58-A, 58-A andadjacent portions of the teeth to coat the entire surface of thesurrounded portions of the varistor with the desired quantity of thevarnish. The varnish also flows inwardly between the two teeth of eachcolumn along the varistor, as viewed in FIG. 18, to entirely fill thesmall space 35 between the diode chips 33-33 due to capillary action.

As the teeth are withdrawn from the proximity of the varistors, thevarnish no longer receives support by adherence to the teeth 58-58 and,therefore, drops are released to flow completely around the varistors31-31. The final result is a shell of varnish 34, as shown in FIGS. 1-3,surrounding the varistors.

LOADING STATION Referring now to FIG. 19, a canistor 51, which isidentical to the canister 51 except that it is empty, is placed on aload station table 158. Alignment of the canister 51 with thecooperating apparatus is obtained in the same manner previouslydescribed for the unload station 44. The racks 37-37 of coated varistorsare pushed along the guide tracks 53-53 onto rack support guides76'-76'. A piston of an air cylinder 159 is connected to the racksupport guides 76'-76 by means of support rods 73-73' which pass throughthe load station table 158.

Latch mechanisms 61-61 are mounted on the load station table 158 at bothends of the canister 51. The latch mechanisms 61-61 consist of latchsupports 162-162 and latches 163-163 which can rotate upward from theirhorizontal position but now downward. The latches 163-163 are longenough to extend into the canister 51 beyond front and rear tie rods 41and 42 of a rack 37 (FIG. 4).

When the piston of the air cylinder 159 moves upward, it lifts the rack37 by means of the support rods 73'73' and the rack support guides76'-76'. The upward movement ofa rack 37 causes its front and rear tierods 41 and 42 to engage the latches 163-163 and rotate the inner endsupward. When the rack 37 has been raised far enough, its tie rods 41 and42 clear the ends of the latches 163-163 permitting the latches 163-163to fall back (rotate). of their own weight to the horizontal position.When the piston of the air cylinder 159 is retracted, the rack 37descends until its front and rear tie rods 41 and 42 rest on the tops ofthe latches 163-163. The racks 37-37 previously lifted remain supportedat a level higher than the top of the next rack 37 which will enter thecanister 51'. The piston of the air cylinder 159 continues to descenduntil the rack support guides 76'76' are in aligned position with guidetracks 53-53 to receive another rack 37.

AUTOMATIC OPERATION ELECTRICAL CIRCUIT The automatic operation of thevarnish apparatus can be understood best in conjunction with theelectrical schematic FIG. 20, the cam chart FIG. 21, and the airschematic FIG. 22.

In operation, when a master selector switch 164, FIG. 20, is turned tothe on position, power is applied to the drive motor 108 of thevarnish-applying station 48. The drive motor 108 then rotates thedriving member 112 continuously (see FIG. 15) as long as the masterselector switch 164 is in the on position. The cam 149 holds the limitswitch 151 open during each revolution of the camshaft 113 except for ashort dwell at the start of the cycle as shown by the rack advance camdiagram in FIG. 21.

The apparatus, in the preferred embodiment, is set in automaticoperation by turning a selector switch 166 (FIG. 20) to the automaticposition, which disconnects a manual push-button switch 167 from thecircuit and connects the interlock limit switch 104 (FIG. 12) into thecircuit. Since the piston of the rack transfer air cylinder 91 is in itsretracted position, the interlock limit switch 104 is held closed by theinterlock cam 106 (see FIG. 10). The limit switch follower 152 rests inthe notch 153 (FIG. and, therefore, the limit switch 151 is closed. Thisestablishes a current path through the switches 104, 166, and 151 and asolenoid 168, as shown in FIG. 20. Energizing the solenoid 168 actuatesair valves which admit air to the racktransfer cylinder 91 and cause theracks 37-37 to be transferred one position to the right. When the pistonof air cylinder 91 reaches its fully extended position to the right, itactuates an air valve which: (1) causes the piston to return to itsstarting position and (2) causes the pistons of unload and load aircylinders 72 and 159 (FIG. 22) to ascend and descend.

Near the end of the return stroke, to the left, of the piston of aircylinder 91, the interlock cam 106, on the piston rod, closes a limitswitch 107 (FIG. 10) momentarily and energizes the solenoid 154 of thesinglerevolution clutch 114 (see FIG. 15) causing it to drive thecamshaft 113 and the cams 116, 117, 118 and 149 through one revolution.This, in turn, causes the varnish station 48 to go through onevarnish-applying cycle, i.e., apply varnish 34 to one rack 37 of thevaristors 36-36 with the events taking place in the timed relationshipshown in FIG. 21. At the end of the varnishapplying cycle, the limitswitch follower 152 drops into the notch 153 of the rack advance cam149, closes the limit switch 151 and establishes a current path throughthe limit switch 104, the selector switch 166, the limit switch 151 andthe solenoid 168. Energizing the solenoid 168 actuates air valves whichadmit air to the rack transfer cylinder 91, thus repeating the cycle.Cooperation and control of the other apparatus components are I achievedthrough a pneumatic control circuit which is described next.

PNEUMATIC CIRCUIT When the solenoid 168 is energized, refer to FIG. 22,it shifts a valve 171 and admits pilot line air (previously filtered andregulated), flowing from a source P through a load-cylinder valve 172,through the valve 171, to a rack-transfer cylinder control valve 173.This shifts the rack-transfer cylinder valve 173 so that it admits airfrom the source P to the rack-transfer cylinder 91 through a How controlvalve 174 in the uncontrolled direction. The flow control valve 174, andthe other flow control valves, are unidirectional. They permit theunrestricted flow of air in one direction but regulate the flow in theother direction. The admission of air to the rack-transfer cylinder 91advances its piston to the right, withdrawing one rack 37 from thecanister 51 and pushing any other racks one position along the transfertable. During the initial portion of the advance, the pilot valve 99 isheld closed by the speed control cam 98, which is fixed to the pistonrod of the air cylinder 91, so that the air being exhausted from theracktransfer cylinder 91 must pass through a slowadvance flow controlvalve 176 in the controlled direction. Further advance of the piston ofthe rack transfer air cylinder 91 permits the pilot valve 99 to open.When the pilot valve 99 opens, a second exhaust path through a flowcontrol valve 177 is provided in parallel with the flow control valve176. This increases the rate of exhaust and regulates the rapid advanceof the piston of the transfer air cylinder 91.

When the piston of the rack-transfer air cylinder 91 reaches itsextended position to the extreme right, the racks 37-37 have beentransferred one position to the right and the speed control cam 98shifts the pilot valve 103. This admits pilot line air simultaneously tothe rack-transfer air cylinder valve 173, an unload station air cylindervalve 178 and to a timer valve 179 through a pilot valve 187.

First with respect to the rack-transfer air cylinder valve 173, pilotline air admitted from the pilot valve 103 to the rack-transfer aircylinder valve 173 shifts the valve 173 back to its initial positionwhich admits air to the right side ofthe transfer air cylinder 91. Thiscauses the piston to retract to the left and return to its startingposition. The air cyliner 91 exhausts through the flow control valve 174in the regulated direction so that the speed of the return can becontrolled by this valve.

Second, with respect to the unload-station cylinder valve 178, pilotline air from the pilot valve 103 shifts the unload-station cylindervalve 178 and admits air from the source P to the unload-stationcylinder 72 through a flow control valve 181 in the unrestricteddirection. This causes the piston of the cylinder 72 to rise to the topof its stroke and lift racks 3737 off the escapement fingers 52-52. Asthe piston rises, the exhaust air flows through flow control valve 183in the controlled direction thus permitting the regulation of the speedor ascent of the piston. As the piston nears the top of its stroke, thecam 82, which is fixed to the piston rod, shifts the valve 79. Thisadmits air from the source P to the escapement valve 78 and pilot lineair to the valve 178 and a valve 182. The pilot line air shifts thevalve 183 and connects the escapement air cylinders 7777 to theescapement valve 78.

Completion of the stroke of the piston of the unload air cylinder 72causes the cam 81 to shift the escapement valve 78 which applies airfrom the source P to the escapement cylinders 77-77 through the valve182. The air forces the pistons of the escapement air cylinders 7777 toextend outwardly thus withdrawing the escapement fingers 7171 so theyclear the rack tie rods 41 and 42. The application, by the valve 79, ofthe pilot line air to the unload-station cylinder valve 178, returns thevalve 178 to the position shown in FIG. 2. This applies air from thesource P to the upper end of the unload-station air cylinder 72 througha flow control valve 183 in the uncontrolled direction. Application ofair to the upper end of the unload air cylinder 72 causes its piston todescend and its exhaust to flow through the flow control valve 181 inthe regulated direction, thus providing a means of controlling the speedof descent. As the piston descends, the cam 81 allows the valve 78 toclose. This traps air in the escapement cylinders 77-77 and holds theescapement fingers 71-71 open until the piston of the air cylinder 72descends far enough for the cam 83 to allow the spring re turned valve79 to return to the exhaust position. This, in turn, allows the springreturned valve 182 to return and exhaust the escapement air cylinders77-77. Springs in the air cylinders 77-77 return the pistons and,therefore, the escapement fingers 71-7l. The earns 81 and 82 are fixedin relationship to each other so that the escapement fingers 52-52 areheld apart just long enough for one rack 37 to pass the escapementfingers 7171, as the piston of the unload-station cylinder 72 descends,before the fingers are returned to support the rest of the column ofracks 37-37.

Third, with respect to the timer valve 179, application of pilot lineair by the pilot valve 103 to the pilot valve 187, shifts the valve 187and applies air to the timer valve 179. The timer valve 179 shifts andalso starts the timing. The shifting of the timer valve 173 appliespilot line air to the load-cylinder valve 172, which shifts this valve,and applies air from the source P to the lower end of the load aircylinder 159 through a flow control valve 184 in the unrestricteddirection. This causes the piston of the load air cylinder 159 toascend. The upper end of the air cylinder exhausts through a flowcontrol valve 186 in the regulated direction, thus permitting control ofthe speed of ascent. After an interval, as determined by the setting ofthe timer valve 179, the valve 179 returns to the exhaust position andexhausts the pilot operatedvalve 172 which, in turn, exhausts the loadair cylinder 159 through the flow control valve 184 in the regulateddirection. Adjustment of the flow control valve 184 controls the speedof descent of the piston of the load air cylinder 159.

Since the valve 103, at the end of the stroke of transfer air cylinder91 directs pilot line air simultaneously to the unload air cylindervalve 178, the transfer air cylinder valve 173 and, through the valves187 and 179, the load air cylinder valve 172, the pistons of both theunload and load air cylinders, 72 and 159 respectively, ascend while thepiston of the transfer cylinder 91 returns to its starting position. Atthe top of its stroke, the piston of the unload air cylinder 72 shiftsthe valve 79 which causes the piston to return to the bottom of itsstroke. The piston of the load air cylinder 159 is returned to itsbottom position by the timer valve 179 when it shifts at the end of itstime cycle.

From the foregoing, it can be seen that, when the rack-transfer solenoid168 and its air valve 171 have been actuated, all air cylinders actcooperatively through one cycle. Further, the air cylinder actuationtakes place only when the motor driven cam 149 cooperating with thelimit switch 151 initiates the cycle. The speed with which the cyclesare repeated is controlled by regulating the speed of the drive motor108 by means of the speed control 188.

From the foregoing description, it may be seen that the preferredembodiment of the invention provides a new automatic apparatus ofapplying varnish simultaneously to large numbers of articles, which isimproved over the older methods because it is much faster and does notcontaminate or damage the articles. it is to be understood that variouschanges may be made from the specific details illustrated withoutdeparting from the spirt or scope of the invention.

What is claimed is:

1. Apparatus for applying a coating of liquid to a portion of an articlewithout contacing the article, which comprises:

an applicator member having a recess in one surface, of a size somewhatlarger than the portion of the article to be coated and of a shape suchthat a quantity of the liquid is retained by capillary action uponengaging the member with the coating liquid;

moving means (1) for engaging the members with the coating liquid so asto cause a quantity of the liquid to be retained in the recess, (2) forbringing the member into close, non-contacting proximity with thearticle so that the recess surrounds the portion of the article to becoated and the liquid flows from the applicator member onto the articleto apply the coating, and (3) for withdrawing the member from suchproximity;

means for applying to the article a force which acts in a directionopposite to the force exerted on the article by the applicator memberwhen it is being withdrawn from the proximity of the article; and

means for moving the force applying means into close, noncontactingproximity with the article to apply the force to the article to preventthe article from sticking to the applicator member.

2. Coating apparatus as recited in claim 1, wherein the moving meansoperates to move the applicator member vertically:

1. to dip a lower portion of the member including the recess into a bathof the coating liquid to coat both the recess and surrounding portionsof the member and then to retract the member from the bath; andsubsequently 2. to lower the member into proximity with the article fora time such that a desired amount of the liquid flows onto the articlefrom the recess and surrounding portions of the member, after which themember is withdrawn from proximity with the article.

3. Coating apparatus as recited in claim 2, for use with articles havingparamagnetic portions, wherein the means for applying a force includes amagnet.

4. Coating apparatus as recited in claim 1, for simul taneously coatinga plurality of similar articles, further comprising:

an elongated member having a plurality of members projecting therefromin a comblike array of applicator teeth aligned in a spaced, planar row,the

teeth being spaced such that each tooth picks up a quantity of thecoating liquid and deposits it on a corresponding one of the articles;and means for holding the articles in a spaced array corresponding tothe spacing of the recesses of the teeth. 5. Coating apparatus asrecited im claim 4, wherein the teeth are separated by slots which arelonger than 5 the depth of immersion of the teeth in a bath of theliquid, to prevent the liquid from flowing from one tooth to the nextand thus to ensure that each tooth carries essentially the same amountof liquid.

1. Apparatus for applying a coating of liquid to a portion of an articlewithout contacting the article, which comprises: an applicator memberhaving a recess in one surface, of a size somewhat larger than theportion of the article to be coated and of a shape such that a quantityof the liquid is retained by capillary action upon engaging the memberwith the coating liquid; moving means (1) for engaging the member withthe coating liquid so as to cause a quantity of the liquid to beretained in the recess, (2) for bringing the member into close,non-contacting proximity with the article so that the recess surroundsthe portion of the article to be coated and the liquid flows from theapplicator member onto the article to apply the coating, and (3) forwithdrawing the member from such proximity; means for applying to thearticle a force which acts in a direction opposite to the force exertedon the article by the applicator member when it is being withdrawn fromthe proximity of the article; and means for moving the force applyingmeans into close, noncontacting proximity with the article to apply theforce to the article to prevent the article from sticking to theapplicator member.
 2. Coating apparatus as recited in claim 1, whereinthe moving means operates to move the applicator member vertically: 2.to lower the member into proximity with the article for a time such thata desired amount of the liquid flows onto the article from the recessand surrounding portions of the member, after which the member iswithdrawn from proximity with the article.
 3. Coating apparatus asrecited in claim 2, for use with articles having paramagnetic portions,wherein the means for applying a force includes a magnet.
 4. Coatingapparatus as recited in claim 1, for simultaneously coating a pluralityof similar articles, further comprising: an elongated member having aplurality of members projecting therefrom in a comblike array ofapplicator teeth aligned in a spaced, planar row, the teeth being spacedsuch that each tooth picks up a quantity of the coating liquid anddeposits it on a corresponding one of the articles; and means forholding the articles in a spaced array corresponding to the spacing ofthe recesses of the teeth.
 5. Coating apparatus as recited in claim 4,wherein the teeth are separated by slots which are longer than the depthof immersion of the teeth in a bath of the liquid, to prevent the liquidfrom flowing from one tooth to the next and thus to ensure that eachtooth carries essentially the same amount of liquid.
 6. Apparatus asrecited in claim 5, wherein: the elongated member is arrangedhorizontally so that the teeth depend vertically therefrom; and themoving means operates to move the teeth vertically into and out of thebath of coating liquid, to a depth less than the lengths of the slots,to coat both the recesses and adjacent portions of the teeth but not theentire lengths of the slots.
 7. Coating apparatus as recited in claim 4,for coating spaced portions of the articles, wherein the teeth arealigned in at least two parallel rows, the corresponding teeth in therows forming columns perpendicular to the rows the columns being spacedin accordance with the spacing of the portions of the article to becoated.
 8. Coating apparatus as recited in claim 1, wherein theapplicator member is formed with a flat rectangular face having agenerally semicircular groove formed centrally therein, constituting therecess, such that flat rectangular land areas are provided on eitherside of the groove, which also pick up coating liquid.
 9. Coatingapparatus as recited in claim 8, for coating a plurality of portions ofarticles at the same time, further comprising: an elongated member formounting a plurality of the members in a comblike array of applicatorteeth mounted in a row with the flat faces in a common plane, saidelongated member being provided with slots for separating the teeth,which slots are longer than the depth of immersion of the teeth in thecoating liquid to prevent liquid from flowing from one tooth to another.10. Apparatus for applying a fluid coating to the body of a leadeddevice without physically contacting said body with means other than thefluid to be applied, comprising: an applicator having a tooth with aconcavity therewithin, said concavity having a dimension exceeding onedimension of said body; a reservoir for holding a quantity of fluid tobe applied; means for engaging said applicator tooth with the fluid insaid reservoir and for transporting the tooth, and that portion of thefluid which is retained in the tooth concavity by capillarity, intoclose proximity to the body of the device, to transfer the fluid to thebody without physical contact between the tooth and the body; means forapplying to the device a force which acts in a direction opposite to theforce exerted on the device by the applicator when it is withdrawn fromtHe proximity of the device; and means for moving the force applyingmeans into close, noncontacting proximity with the device to apply theforce to the device to prevent the device from sticking to theapplicator.
 11. Apparatus as recited in claim 10, wherein said devicehas paramagnetic leads and wherein said force applying means hasmagnetic characteristics.
 12. Apparatus as recited in claim 10, forapplying a fluid coating to a double bodied leaded device, wherein saidapplicator has a pair of concave teeth spaced from each other forapplying fluid to both body portions of the device, simultaneously. 13.Apparatus as recited in claim 10, for applying a fluid coating to thebodies of a plurality of leaded devices, simultaneously, withoutphysically contacting any of said bodies with means other than the fluidto be applied wherein: said applicator contains a plurality of spacedteeth, each tooth having a like concavity therewithin, the spacesbetween adjacent teeth being deeper than the depth of a concavity. 14.Apparatus as recited in claim 13, for applying a fluid coating to aplurality of double bodied leaded devices, simultaneously, wherein: saidapplicator comprises two parallel elongated members, each having aplurality of spaced teeth, and connecting means for holding saidmembers, the corresponding teeth of said members being aligned incolumns perpendicular to said members.